Google has just changed its uppercase “G” favicon to a lower-case “g” favicon shows in address bar, in browser's tabs and in the list of bookmarks.
Old favicon New favicon
As with standard size of favicons, the new favicon is 16x16 and hosted under "favicon.ico".
A little bit focusing on why Google changed its favicon makes a lot of sense: Google loves numbers, Google plays with numbers, Google is aiming to be a sense of something that never ends, so the philosophy of eternity and infinity. Regarding this the new favicon interprets infinity "∞". It's just chosen because it was easy to rotate an "8" character by 90° when typesetting was done by hand. The symbol is sometimes called a "lazy eight", evoking the image of an "8" lying on its side.
What Google actually has done is to re-rotate(turn back) the symbol to earlier version, so "∞" to "8" as it was. Beyond this, the "8" interprets the lower-case favicon "g".
Another interpretation is that the infinity symbol is a clear depiction of the hourglass turned 90°. Obviously, this action would cause the hourglass to take infinite time to empty thus presenting a tangible example of infinity. The invention of the hourglass predates the existence of the infinity symbol allowing this theory to be plausible.
Well, Google never ends ...